Nickel-supported metal-carbon nanocomposites: New catalysts of hydrogenation of phenylacetylene

Nickel-containing metal-carbon nanocomposites (Ni@C) synthesized by levitation melting in a flow of an inert gas-hydrocarbon mixture were used as catalysts of the hydrogenation of phenylacetylene (PA). The nanocomposites were characterized by X-ray photoelectron spectroscopy, simultaneous thermal analysis, and temperature-programmed reduction. The nickel-carbon nanocomposites were stable on storage in air, with only 13% of the total amount of nickel oxidized after 3.5 years of storage. In addition to nanoparticles completely covered with carbon, the composites contained partially coated metal particles, which are readily oxidized in air. Both types of particles exhibited the catalytic activity in phenylacetylene hydrogenation. At higher contents of nickel partially coated with carbon, the activity increased and the selectivity of styrene formation decreased. The minimum half-conversion temperature (75A degrees C) was determined for a specially prepared Ni@C sample with an increased content of oxidized nickel (28%). The maximum selectivity of styrene formation (similar to 75% at 150A degrees C) was recorded in the presence of the sample with the smallest amount of oxidized nickel (less than 4%).